svoid drawRecognitionGrid(Graphics2D g, RecognitionGrid grid) {
  if (g == null || grid == null) ret;
  for (int row = 0; row < grid.rows; row++)
    for (int col = 0; col < grid.cols; col++) {
      RecognitionGrid.Cell c = grid.getCell(col, row);
      if (c == null) continue;
      Rect r = grid.cellRect(col, row);
      fillRect(g, r, colorFromRGBA(c.outerColor));
      fillRect(g, shrinkRect(r, iround(r.w/6)), colorFromRGBA(c.middleColor));
      fillRect(g, shrinkRect(r, iround(r.w/3)), colorFromRGBA(c.centerColor));
    }
}